[Halld-cal] [GlueX] PrimEx D preparation

Fri Nov 16 19:11:04 EST 2018

Hi Matt,

For reference, Ilya, can you provide the gain constants relative to the
> nominal constants that you obtained for the inner two layers?  These are
> masked in the trigger, so HV modifications here would be minimally invasive
> to the GlueX run, but may give us a chance to calibrate the blocks after
> the change.
>

 We talked after you left about implementing this. I should be able to get
the HV modification done with relative ease with new constants.

-Colin

On Fri, Nov 16, 2018 at 6:46 PM Shepherd, Matthew <mashephe at indiana.edu>
wrote:

>
> Sasha and Ilya,
>
> I apologize for having to leave abruptly this afternoon (our preschool has
> strict pickup times).
>
> The progress that Ilya showed in reconstructing pi0's with the inner
> blocks is very nice!
>
> It seems the clear issue here is the behavior of the two clusterizing
> algorithms.  If the standard algorithm reconstructed clusters around the
> beam hole the blocks then we would have easily calibrated these and not be
> discussing it.  Further, it seems also the failure of the standard
> algorithm is a result of noise as there is a correlation between occupancy
> and blocks with no clusters.
>
> Ilya:  can you outline or share the various settings of your clustering
> algorithm?  I suspect it is semi-standard where you look for a high energy
> "seed" and then add blocks to the seed.  For example, what is your seed
> threshold?  How are you using timing of hits?  Could you please share the
> specifics of the algorithm or point us to the code you use?
>
> This is all very relevant as we discuss the reconstruction launch of the
> Spring 2018 data.  If we are able to make small modifications to recover
> some tiny bit of acceptance in the inner region, then it would be worth
> doing.  It could be as simple as adjusting the seed threshold in the
> standard algorithm.
>
> I am in favor of trying to adjust HV to balance gains of inner blocks.  We
> may consider this prior to the end of the current GlueX run so that we may
> acquire some new data (subject to discussion with everyone else).  For
> reference, Ilya, can you provide the gain constants relative to the nominal
> constants that you obtained for the inner two layers?  These are masked in
> the trigger, so HV modifications here would be minimally invasive to the
> GlueX run, but may give us a chance to calibrate the blocks after the
> change.
>
> I suspect that measuring Compton at the precision you desire will require
> all of these be balanced.  I think the sooner we can get to that point, the
> better.
>
> Regarding the outer layers:
>
> I'm much less convinced that the gain constants there are meaningful.  My
> suspicion is that your systematic high shift of gains is just shifting the
> standard noise peak at gamma gamma mass threshold  to the pi0 location.  It
> seems very hard to believe all of the channels on the outside somehow have
> systematically underestimated gains by a factor of 5-10.
>
> To clearly answer Sean's question regarding geometry, I attach a view
> (generated in 2006) of the *design* gap between the FCAL and BCAL.  This
> view is drawn from the downstream end of the target (minimal case for BCAL
> "shadowing" of FCAL).  The innermost circle represents how the inner radius
> of the BCAL at the downstream end projects onto the FCAL.  Beyond the end
> of the BCAL there are of course light guides, SiPMs, cables, etc. that will
> all further shadow the FCAL.  The true overlap for photons coming from the
> center of the target is more significant.  I suspect calibrating the outer
> layer with photons originating from the target that have the majority of
> their energy deposited in a block in the outer layer is impossible.
>
> Finally, I would like to be able to participate in your meetings.  Please
> keep me up to date regarding schedules.
>
> Matt
>
>
>
>
> On Nov 15, 2018, at 11:03 PM, Alexander Somov <somov at jlab.org> wrote:
>
> Dear Colleagues,
>
> We are going to start discussing aspects critical for the PrimEx D
> experiments, such as
>
> - performance of the FCAL, luminosity determination, etc.
>
> during some of our weekly PrimEx D meeting. So far, we have mostly been
> focused on construction details of the Compton Calorimeter. The next
> meeting
> will take place tomorrow (November 16) in Hall D counting room at 4 pm.
>
> BlueJeans connection: https://www.bluejeans.com/7572695553
> <https://urldefense.proofpoint.com/v2/url?u=https-3A__www.bluejeans.com_7572695553&d=DwMGaQ&c=lz9TcOasaINaaC3U7FbMev2lsutwpI4--09aP8Lu18s&r=VNruI5B3_Ie9AiOp0_GgpPscd-lfGLx1DNIPlMbQfwQ&m=tEnmUAGm3JkGTILHapYfLvRyW1MIaj79ELC-ro1TPAY&s=Gaqpj1imnGeSbXmDAFM8sO5OnLp2CJyFr_5qDQtWzqU&e=>
> Meeting ID: 7572695553
>
> The main topic for discussions:
>
> - calibration of the FCAL
>
>   (some significant progress has been done in this direction, you will be
>                           surprised to see … )
>
> The meeting page will be available shortly.
>
>
> --------
>
> We have created a mailing list  primexd at jlab.org for future
> communications.
> In order to subscribe, send an email to:
>
> primexd-request at jlab.org
>
> Subject: subscribe
>
>
>
> Cheers,
>       Sasha
>
> _______________________________________________
> GlueX-Collaboration mailing list
> GlueX-Collaboration at jlab.org
> https://mailman.jlab.org/mailman/listinfo/gluex-collaboration
>
>
> _______________________________________________
> Halld-cal mailing list
> Halld-cal at jlab.org
> https://mailman.jlab.org/mailman/listinfo/halld-cal

-- 
Colin Gleason
Postdoctoral Fellow
Indiana University
Department of Physics
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://mailman.jlab.org/pipermail/halld-cal/attachments/20181116/c45c752f/attachment-0001.html>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: bcal_fcal_overlap.gif
Type: image/gif
Size: 22520 bytes
Desc: not available
URL: <https://mailman.jlab.org/pipermail/halld-cal/attachments/20181116/c45c752f/attachment-0002.gif>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: bcal_fcal_overlap.gif
Type: image/gif
Size: 22520 bytes
Desc: not available
URL: <https://mailman.jlab.org/pipermail/halld-cal/attachments/20181116/c45c752f/attachment-0003.gif>